1. Field of the Invention
The present invention is directed to a magnetic tape unit having a single-reel magnetic tape cartridge (i.e., a cartridge having only one reel with a magnetic tape wound thereon, hereinafter referred to as a cartridge) to be used in a computer system file. Particularly, the present invention is directed to an apparatus for threading and unthreading magnetic tape in a cartridge in a magnetic tape unit.
A cartridge is first loaded into a magnetic tape unit. The magnetic tape is then threaded through a threading path and wound on a machine reel of the magnetic tape unit to establish a running path for the magnetic tape. A write or read operation is then performed on the magnetic tape.
With an ever-increasing demand for a small-sized computer system, the demand for a small-sized magnetic tape unit is also increasing. It is an absolute necessity for attaining high reliability that a magnetic tape unit securely perform threading and unthreading of the magnetic tape. Therefore, a small-sized magnetic tape unit threading apparatus is in great demand.
2. Description of the Related Art
FIG. 1, including FIGS. 1(a)-1(c), is a diagram of an outline of a magnetic tape cartridge. FIG. 1(a) is a perspective view of a magnetic tape cartridge; FIG. 1(b) is a sectional view of the magnetic tape cartridge with a leader-block ready to be inserted therein; and FIG. 1(c) is a sectional view of the magnetic tape cartridge with the leader-block inserted therein.
In FIGS. 1(a)-1(c), a single -reel cartridge 1 has a reel with a magnetic tape 2 wound thereon. The end of the magnetic tape 2 is connected to a leader-block 3 which has an opening 3b used for pulling the leader block 3 and thus the magnetic tape 2 out of the cartridge 1. The leader-block 3 is inserted and latched in the cartridge 1.
When the leader-block 3 is pushed into the cartridge opening in the state shown in FIG. 1(b), the tongue 3a of the leader-block 3 rides on and across the cartridge tongue 1a, which is molded synthetic resin, and is latched thereon as shown in FIG. 1(c).
The cartridge tongue 1a has a spring property and supplies a repulsive force when the leader-block 3 is pushed into or pulled out of the cartridge 1. For instance, the ANS Standard stipulates that the insertion force F required to push the leader-block into its latched position in the cartridge should not exceed 1.23 kg.
FIG. 2 is a schematic diagram of a prior art magnetic tape threading mechanism. In FIG. 2, the chain line T is the path along which a magnetic tape is threaded and M is a threading motor.
When the cartridge 1 is loaded in a magnetic tape unit, the magnetic tape 2 is pulled out of the reel of the cartridge 1 and input to the machine reel 4 after being threaded through a tape guide 12a, a magnetic head 13, a tape guide 12b and a tension roller 14.
A panto-arm consisting of a first arm 6, second arm 7, third arm 9 and fourth arm 10 threads the magnetic tape 2. As the panto-arm swings, a pin 8 provided at an end of the panto-arm pulls out the leader-block 3 which is provided at the end of the magnetic tape 2. A guide pin 11 of the panto-arm moves along the guide groove 5a to the machine reel 4 to engage the leader-block 3 with the leader-block groove 4a of the machine reel 4.
The above sequence is reversed for unthreading the magnetic tape. When a flag 16 attached to the second arm 7 comes in front of a photosensor 15, the photosensor 15 detects that the leader-block 3 is inserted and causes the panto-arm to stop swinging.
Accordingly, the conventional threading mechanism has the following problems.
(1) In a threading mechanism using a panto-arm, the magnetic tape has to travel over a long tape path, which makes the magnetic tape unit large in size. PA1 (2) A large insertion force F is required to insert the leader-block 3 into the cartridge 1. To get an insertion force F large enough, the panto-arm must be swung at a high rotational speed at the moment the leader-block 3 is inserted into the cartridge 1. The leader-block insertion, however, may fail if the panto-arm rebounds due to a repulsive force acting on the leader-block 3. PA1 (3) The leader-block insertion may fail due to a dimensional error in the cartridge 1 or a positioning error of the cartridge 1 when loaded into the magnetic tape unit. PA1 (4) Even when the leader-block insertion fails, the above-mentioned photosensor 15 may erroneously detect the flag 16 and incorrectly determine that the leader-block 3 is securely inserted in the cartridge 1. As a result, the magnetic tape unit will malfunction and the computer system will be halted.
The following prior art references are representative of threading apparatuses: Japanese Laid-Open Patents Provisional Publication Nos. 62-257657, 62-119765, 60-10446 and 63-10360.
No. 62-257657 suggests an automatic tape loading mechanism including a tape guide with a difference in level and a spring. The spring absorbs shake and shock which occur when the arm moves along the tape guide.
No. 62-119765 suggests an automatic tape threading device including a linkage of two arms and a guide groove. This reference, however, does not teach the elastic member of the present invention.
No. 60-10446 suggests a magnetic tape threading device which threads a magnetic tape by guiding a linkage arm assembly along a guide groove (cam track means). This reference, however, does not teach the elastic member of the present invention.
No. 63-10360 suggests a tape drive device including a threading arm which consists of a linkage of two arms and has a threading motor connected at an end and a pin for pulling the leader-block. This reference, however, does not teach the elastic member of the present invention.